Potassium deficiency

Specific potassium (K) deficiency symptoms always appear in the oldest leaves of whweat, although growth of the whole plant can be affected prior to symptoms with all leaves having an unthrifty and spindly appearance. Under severe K deficiency, necrosis in the oldest leaves begins as a necrotic speckling along the length of the leaf, spreading quickly to the tip and the margins. As a result of this spread of necrotic tissue, an arrow of green tissue from the base upwards towards the center can remain.

Chlorotic tissues, generally seen as a mottling, turn necrotic rapidly with K deficiency (in contrast to nitrogen deficiency). Complete death of old leaves is common and plants in the field may appear to have dried prematurely due to drought stress. Magnesium and potassium deficiencies in wheat also result in plants appearing unthrifty and drought stressed and in reduced 1000-grain weight. Potassium deficiency can be difficult to detect, and yield losses can occur long before visual symptoms appear.

K deficiency may occur within specific areas in a field associated with deep leaching sands, livestock feedlots, and the removal of hay and other above-ground plant material. Crops severely affected appear drought-stressed with large numbers of prematurely dead, old leaves, and spindly growth.